NUMERICAL RELATION AND 3D MODELLING OF

HUMAN HEAD BALANCE FACTORS

VAHID GOODARZY

DISSERTATION SUBMITTED IN FULFILMENT OF

THE REQUIREMENTS FOR THE DEGREE OF

MASTER OF PHILOSOPHY

INSTITUTE OF GRADUATE STUDIES

UNIVERSITY OF MALAYA

KUALA LUMPUR

2016

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ORIGINAL LITERARY WORK DECLARATION FORM

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Abstract

The visual, vestibular, and proprioceptive systems make up the physiological balance

sensory system which is essential in maintaining balance and stability of a human body.

In biomechanical analysis, forces around the centre of gravity affect movement and

stability. The head centre of gravity (CG) which crosses three main planes (sagittal,

frontal and transverse) is an important area related with balance. Previous researches have

associated the head sensory systems with balance, however mathematical relations

between these balance factors and CG have not been established. The main aim of the

study was to establish mathematical relation using distances and angles between the head

sensory systems (visual and vestibular) and CG, and used these values to design a novel

3D model of a human head. The secondary aim of the study was to introduce photography

(PH) as a new technique to locate the head sensory system’s anatomical landmarks and

validate this using computer aided tomography (CT).

Three methods were employed; (i) CT - to locate the CG and exact anatomical location

of visual and vestibular systems, (ii) PH - to locate the surface anatomical landmarks of

head sensory systems, and (iii) anthropometric devices to calculate the head volume.

In order to calculate the mathematical relationships between the head sensory systems,

the balance factor line (BFL: the line connecting visual and vestibular systems) was

illustrated. The average distance between the visual and vestibular lines (DVV) on both

sides; for CT and PH are 8.16 ± 0.35 cm, and 8.11 ± 0.58 cm respectively, while the angle

between the BFL and the Frankfort plane (AVVF) on both sides; for CT and PH are 11.80

± 0.25o, and 11.65 ± 0.45o respectively. The comparison for angle of AVVF between left

and right sides has r value of 0.98, while P < 0.001. These values showed that there was

no significant difference between CT and photos. The intraclass correlation coefficient

between two ratters which shows the reliability of the methods was 0.970 for the CT

images and 0.960 for PH. Based on the 3D modelling, an imagery plane which connects

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the left and right head balance factors was drawn. The head CG was represented as a

hollow sphere in this model, and the connection between the CG and the imaginary plane

formed pyramidal structure.

CT scan imaging is hazardous and expensive and also the equipment is not easy to access,

thus, this new method is hypothesised as a viable alternative compared to previous

approaches that yield outcomes similar to those of the CT images. The proposed

imaginary plane connecting the human balance factors is not parallel with the existing

planes.

Applying this new 3D model of the human head, the mathematical relationships between

the head CG and the imaginary plane could be used in biomechanical analysis of human

balance and stability.

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Abstrak

Daya penglihatan / visual, bahagian dalam telinga atau vestibular, dan sistem pergerakan

badan atau sistem proprioceptive memainkan peranan penting dalam membentuk

keseimbangan sistem fisiologi deria di samping mengekalkan keseimbangan dan

kestabilan badan manusia. Dalam analisis biomekanik, tekanan kuasa di sekitar pusat

graviti mempengaruhi pergerakan dan kestabilan tubuh badan. Pusat graviti (CG) yang

melintasi tiga satah utama (sagittal, frontal dan melintang) merupakan kawasan penting

yang berkaitan dengan keseimbangan tubuh. Kajian sebelum ini telah dikaitkan dengan

keseimbangan sistem deria kepala namun kedudukan matematik di antara faktor

keseimbangan dan CG belum wujud lagi. Matlamat utama kajian ini adalah untuk

membina kedudukan matematik dengan menggunakan jarak dan sudut di antara sistem

deria kepala (visual dan vestibular) dan CG, malah nilai tersebut digunakan untuk

mereka-bentuk model 3D kepala manusia. Tujuan kedua kajian ini adalah untuk

memperkenalkan fotografi (PH) sebagai satu teknik baru bagi mengesan lokasi anatomi

sistem deria kepala malah memperakui kajian ini menerusi tomografi berkomputer (CT).

Tiga kaedah telah digunakan iaitu; (i) CT - untuk mengesan CG dan lokasi tepat anatomi

sistem visual dan vestibular, (ii) PH - untuk mengesan lokasi anatomi sistem deria pada

permukaan kepala, dan (iii) menggunakan peranti antropometri untuk mengira kandungan

isi padu kepala.

Dalam usaha mengira kedudukan matematik di antara sistem deria kepala, garis faktor

keseimbangan (BFL: garis yang menyambungkan sistem penglihtan / visual dan

vestibular) telah ditunjukkan. Purata jarak antara baris / garis visual dan vestibular (DVV)

di kedua-dua belah menunjukkan CT dan PH adalah pada paras 8.16 ± 0.35 cm, dan 8.11

± 0.58 cm, manakala sudut di antara BFL dan satah Frankfort (AVVF) di kedua-dua

bahagian; masing-masing menunjukkan CT dan PH pada paras 11.80 ± 0.25o dan 11.65

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± 0.45o. Perbandingan sudut AVVF antara sisi kiri dan kanan pula menunjukkan nilai r

pada aras 0.98, manakala P

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Acknowledgments

First and foremost I want to thank my advisor Dr. Ashril Yusof and Prof. Azuan Abu

Osman, It has been an honor to be his master student. Who strongly support me to do

good experimental research in biomechanics. I appreciate all those contributions of time,

ideas, and funding to make my master experience productive and stimulating.

I would like to take this opportunity to express my grateful to Prof. Khyrol Azmi for

allowing me to be in PPUM biomedical imaging department and use the CT scan images

of patients and other staff there who were kind to me.

I gratefully acknowledged the funding sources that made my master work possible. I was

funded by the HIR for my first 2 years and was honored to be a HIR candidate. My time

at UM was made enjoyable in large part due to the many friends and groups that became

a part of my life.

The members of the postgraduate group of sport center faculty have contributed

immensely to my personal and professional time at University Malaya. The group has

been a source of friendships as well as good advice and collaboration.

Lastly, I would like to thank my family for all their love and encouragement. For my

parents who raised me with a love of science and supported me in all my pursuits. For the

presence of my brother Farhad which strongly encourage me to continue this research.

And most of all for my loving, supportive, encouraging, and patient wife Sara whose

faithful support during the final stages of this master is so appreciated. Thank you.

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TABLE OF CONTENTS

Abstract ------------------------------------------------------------------------------------------i

Abstrak ------------------------------------------------------------------------------------------iii

Acknowledgements ----------------------------------------------------------------------------iv

List of figures ----------------------------------------------------------------------------------ix

List of tables -----------------------------------------------------------------------------------x

List of symbols and abbreviations ----------------------------------------------------------x

CHAPTER 1 INTRODUCTION

1.1 INTRODUCTION ................................................................................................. 2

1.1.1 BALANCE CONTROL SENSORY SYSTEMS ........................................................... 2

1.1.2 ANATOMICAL LANDMARKS OF THE HEAD BALANCE SYSTEM ........................... 5

1.1.3 THE HEAD CENTRE OF GRAVITY (CG) AND PLANES .......................................... 6

1.1.4 MODELLING OF THE HEAD ............................................................................... 8

1.2 PROBLEM STATEMENT .................................................................................... 9

1.3 OBJECTIVES OF STUDY .................................................................................. 10

1.4 SIGNIFICANCE OF STUDY ............................................................................. 10

2.1 HUMAN BALANCE SENSORY SYSTEM ....................................................... 12

2.2 BIOMECHANICS OF HUMAN BALANCE ..................................................... 14

2.3 HUMAN HEAD PLANES AND CENTRE OF GRAVITY (CG) ...................... 15

2.4 ANATOMICAL LANDMARKS ........................................................................ 17

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2.5 3D AND MATHEMATICAL MODELLING OF HUMAN HEAD ................... 20

3.1 APPROACH AND SELECTION OF RESEARCH METHODOLOGY

(RESEARCH DESIGN) ................................................................................................. 23

3.2 SUBJECTS ........................................................................................................... 23

3.3 ETHICAL CONCERN AND HOSPITAL POLICY ........................................... 24

3.4 FLOW CHART .................................................................................................... 24

3.5 COMPUTER TOMOGRAPHY ........................................................................... 26

3.5.1 DETERMINING ANATOMICAL LANDMARKS ..................................................... 27

3.6 PHOTOGRAPHY ................................................................................................ 27

3.6.1 DETERMINING ANATOMICAL LANDMARKS ..................................................... 29

3.7 ANTHROPOMETRIC MEASURES................................................................... 29

3.8 COMPUTER MODELLING OF HUMAN HEAD ............................................. 30

3.9 MATHEMATICAL RELATIONSHIP ................................................................ 31

3.10 STATISTICAL ANALYSIS ............................................................................ 31

4.1 DEMOGRAPHICS DATA .................................................................................. 33

4.2 DISTANCE AND ANGLE FROM CT IMAGES ............................................... 34

TABLE 4.2.1 PARAMETERS OBTAINED FROM CT SCAN IMAGES. .................. 34

4.3 DISTANCE AND ANGLE FROM PHOTOGRAPHY ....................................... 35

TABLE 4.3.1 PARAMETERS OBTAINED FROM PHOTOGRAPHY (PH) IMAGES.

......................................................................................................................................... 35

4.4 DISTANCE AND ANGLE USING ANTHROPOMETRIC DEVICES ............. 36

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TABLE 4.4.1 PARAMETERS OBTAINED USING ANTHROPOMETRIC DEVICES.

......................................................................................................................................... 36

4.5 STATISTICAL ANALYSIS ................................................................................ 36

4.5.1 CORRELATIONS .................................................................................................... 36

4.5.2 ANALISIS OF VARIANCE (ANOVA) ..................................................................... 37

4.5.3 INTRACLASS CORRELATION (ICC) BETWEEN RATTERS ........................................ 37

4.6 IMAGINARY PLANE ........................................................................................ 38

4.7 3D MODELLING ................................................................................................ 40

5.1 INTRODUCTION .................................................................................................... 43

5.2 ANATOMICAL LANDMARKS AND THE PROPOSED PLANE. ....................... 43

5.3 3D MODELLING OF HUMAN HEAD ................................................................... 46

5.4 MATHEMATICAL MODEL BETWEEN HUMAN HEAD FACTORS ................ 48

5.5 LIMITATION OF STUDY ....................................................................................... 50

5.6 FUTURE STUDY ..................................................................................................... 50

5.6 PRACTICAL APPLICATION ................................................................................. 51

5.7 CONCLUSION ......................................................................................................... 51

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List of figures

CHAPTER 1 INTRODUCTION

Figure 1.1.1 1 Visual system and cerebellum cortex ........................................................ 3

Figure 1.1.1 2 Vestibular system and cerebellum cortex .................................................. 5

Figure 1.1.2. Human head anatomical landmarks ............................................................. 6

Figure 1.1.3.1 Head and neck centre of gravity ................................................................ 7

Figure 1.1.3.2 Human head planes .................................................................................... 8

Figure 1.1.4 Human head 3D modelling using SolidWorks 2014 .................................... 9

CHAPTER 2 LITERATURE REVIEW

Figure 2 1 Human body balance mechanism .................................................................. 14

CHAPTER 3 METODOLOGY OF RESEARCH

Figure 3.4 Flowchart showing the research process ....................................................... 25

Figure 3.5 The left and right side of CT images ............................................................. 27

Figure 3.6 The camera and seat position ......................................................................... 28

Figure 3.7 The head volume calculation (V = 4/3 πabc.) ............................................... 30

CHAPTER 4 RESULTS

Figure 4.6 1 Sagittal view of planes ................................................................................ 38

Figure 4.6 2 Top view of planes...................................................................................... 39

Figure 4.6 3 Front view of planes ................................................................................... 39

Figure 4.6 4 Schematic view of imaginary plane of human head balance factors .......... 40

Figure 4.7.1 Lateral view of 3-D model .......................................................................... 41

Figure 4.7.2 Left and top view of 3D model ................................................................... 42

Figure 4.7.3 Close-up view of CG and visual-vestibular pyramid ................................. 42

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CHAPTER 5 DISCUSSION

Figure 5.3 1 Polygonal model of human head ................................................................ 48

Figure 5.3 2 Curve model of human head ....................................................................... 49

Figure 5.4.1 Imaginary plane.. ........................................................................................ 50

List of tables

Table 4.1 1 Demographic of subject’s characteristics .................................................... 33

Table 4.2.1 Parameters obtained from CT scan images. ................................................. 34

Table 4.3.1 Parameters obtained from photography (PH) images .................................. 35

Table 4.4.1 Parameters obtained using anthropometric devices ..................................... 36

Table 4.5.1 Pearson correlation (r value) between CT and PH images .......................... 37

CT = Computer aided tomography

PH = Photography

BFL = The line connecting visual and vestibular systems

DVV = Distance between the visual and vestibular lines

AVVF = Angle between the visual-vestibular lines and the Frankfort plane

TBD = Distance from top to bottom of eye

THVID = Distance between the top head (forehead) to the eye

THVED = Distance between the top head (forehead) to the ear

BHVED = Distance between the head bottom and the ear

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CHAPTER 1

INTRODUCTION

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1.1 Introduction

The main purpose this chapter is to provide relevant information within the scope

of this research such as definition of parameters to ease readers into the following

chapters. This chapter introduces the parameters and systems which are exploited in this

research such as the explanation of human balance control, head centre of gravity,

anatomical landmarks, human head planes and 3D modelling of the head.

1.1.1 Balance control sensory systems

Human balance and stability are affected by the physiological balance system,

nervous system, and reaction time. In order to sustain human balance and ensure that the

brain receives appropriate information, several mechanisms are employed namely the

three physiological sensory systems which are: visual, vestibular and proprioceptors and

nervous systems. Previous studies emphasise the human head as the main control centre

of balance. The visual, vestibular, and proprioceptive systems comprise the sensory

system of physiological balance in humans, which is essential to the maintenance of

balance and stability (Horak et al., 1990; Day et al., 1997; Carpenter et al., 2001; T.

Mergner et al., 2009; Naito et al., 2012). The visual and vestibular systems are located in

the head, and the proprioceptors are situated at the sole, ankle, and knee joints.

Head sensory system serves an important function in human balance and stability

(Beier et al., 1979; Winter, 1995). When the human head changes position or the body

loses stability, the sensory system sends information to the cerebellum and brain, where

the signals are analysed; subsequently, appropriate orders are sent to muscles and joints

to restore stability (Mort et al., 2003; Mathie et al., 2004; Chiu, 2005).

The vision influences balance by reacting to motion as a relative image shifts onto

the retina (Paulus et al., 1984), whereby it triggers the muscle activation required for

postural corrections to take place. The efficiency of vision in postural control depends on

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visual acuity (Paulus et al., 1984), visual contrast (Leibowitz et al., 1979), object

distances (Paulus et al., 1984) and room illumination. For instance, visual acuity, contrast

sensitivity and depth perception play significant roles in the ways in which humans

themselves can see objects with clarity. Environmental factors, such as room lighting

affect the individuals in seeing their surroundings. Furthermore, previous literature has

indicated that humans demonstrate diminished ability to control posture in low-light

conditions (Owsley & Sloane, 1987; Lord & Menz, 2000). It is believed that many

internal factors, such as age and gender as well as many external factors like environment

affect the human balance system.

Figure 1.1.1.1 Visual system and cerebellum cortex (Wiley, 2009).

The vestibular organs known as balance organs of the inner ear, serve this

complex motor function at a largely subconscious level but their role does not stop with

balance. The value of the vestibular sensory system to brain functions such as perception

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of self and non-self-motion, spatial orientation, navigation, voluntary movement,

coulometer control and autonomic control comes from their unique and complete

description of head motion and orientation in three dimensions (Peterka, 2002; Zhang et

al., 2011; Naito et al., 2012).

Inner ear is a place in the skull which includes vestibular, semicircular canal and

cochlea (Allum & Honegger, 1994; Zhang et al., 2011). The vestibular organs are

responsible for sending messages continuously to the brain for accelerations, how the

head is rotating and translating its orientation in space. Even when we are completely

immobile, the messages never stop and the signals relentless pull of gravity. Perhaps

because of their constant monologue, the vestibular sensation acts differently to the other

senses. On the other hand, there is no obvious recognisable conscious sensation from

these organs, which can provide a silent sense (Mergner et al., 1991; Maurer et al., 2000;

Carpenter et al., 2001; Cathers et al., 2005; T. Mergner et al., 2009).

Figure 1.1.1.2 Vestibular system and cerebellum cortex (Timothy C. Hain,

2012).

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1.1.2 Anatomical landmarks of the head balance system

Anatomists use specific terms to indicate areas of the body, such as the cephalon

or cephalic region that refers to the head. This region is further differentiated into more

specific areas, including the cranium (skull), facies (face), frons (forehead), oculus (eye

area), auris (ear), bucca (cheek), nausus (nose), oris (mouth), and mentis (chin) (Clauser

et al., 1969; Beier et al., 1979; Dumoulin et al., 2000; Chiu, 2005). These points are

known as standard landmarks on the surface of the human body, and some of them are

the external counterparts of internal anatomical points (Beier et al., 1979; Ringelstein et

al., 1990; Hughes, 2007; Subburaj et al., 2009).

Figure 1.1.2 Human head anatomical landmarks.

Several methods have been used to identify anatomical landmarks, including X-

ray and magnetic resonance imaging (MRI). The images taken by computed tomography

(CT) have been also subsequently used to locate precisely the anatomical landmarks on

the surface of the human body, and this technique has been proven to be reliable (Bernick

et al., 2001; Karch, 2004; Mikaeloff et al., 2004; Haruna et al., 2010). CT provides a 3D

view of the anatomical landmarks. Even minor parts/organs of the body can be precisely

viewed so that researchers can observe the organs in various layers and levels (Ringelstein

et al., 1990; Chiu, 2005; Hughes, 2007; Haruna et al., 2010).

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1.1.3 The head centre of gravity (CG) and planes

The head also contains an area called the head centre of gravity (CG), which is a

significant point for biomechanical analysis (McConnell et al., 1995; Willinger et al.,

1999; Funk et al., 2009; Yoganandan et al., 2009). Dempster (1955) reported that the CG

is located along a point in the phenoid sinus averaging 4mm beyond the anterior-inferior

margin of the sella; on the surface its projections lay over the temporal fossa on or near

the nasion-inion line at a point about 32 % back from the nasion; it was equally distant

above the zygomatic arch and behind the malar fronto-sphenoid process. Winter and his

team (1995) demonstrated that CG landmarks are anatomically located above the right

and left infraorbital notches and at the superior edge of the right and left external auditory

meatus on the skin. These landmarks originate from the centre of the markers of the right

and left external auditory meatus. The +Z axis extends from the origin in a cephalad

direction to the plane formed by the +X axis and the line between the auditory meatus

markers at right angles. The +Y axis extends from the origin toward the left ear to the X–

Z plane at right angles. This plane is known as the mid sagittal plane. The anatomical

location of the head and neck CG is “8 mm anterior to the basion on the inferior surface

of the base of Occiput or within the bone 24 ± 5 mm from the crest of the dorsum sella;

on the surface of the head a point 10 mm anterior to the supratragic notch above the head

of the mandible is directly lateral.” Clauser and his team (Clauser et al., 1969) reported

that the mean distances of the head CG are 46.4% below the vertex and 40.0% from the

occiput.

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Figure 1.1.3.1. Head and neck centre of gravity (Sazer, 1995).

Three main planes cross the human head, namely, the Frankfort (transverse),

sagittal (sagittal), and coronal (frontal) planes (Clauser et al., 1969; Keshner & Peterson,

1995). The Frankfort plane passes through the inferior margin of the left orbit (the left

orbitale) and the upper margin of each ear canal or the external auditory meatus (the

porion). It is almost parallel to the ground. The sagittal plane is a vertical plane that

extends from the ventral (front) to the dorsal aspect (rear) and divides the head into right

and left halves. The coronal plane is a vertical plane that divides the head into ventral

(belly) and dorsal (back) sections (Clauser et al., 1969; Ringelstein et al., 1990; Koo &

Kim, 1995; Volinsky et al., 1997; Dougherty et al., 2003).

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Figure 1.1.3.2 Human head planes.

.

1.1.4 Modelling of the head

The collection and application of anthropometric data within digital human

modelling systems raises many questions. Often the data will have been collected for

direct use in a particular design application and may not meet the more generic needs of

human modelling systems. There is a consequent need for some transformation to for

example convert the external body dimensions normally collected in anthropometric

surveys into the internal joint-to-joint dimensions that form the basis of most models.

Perhaps, the most significant problem arises from the use of a ‘percentile’

approach that is in conflict with the multivariate nature of anthropometric data. Fifth

and ninety-fifth percentile models are commonly used in the belief that this will

‘accommodate’ an appropriate proportion of the user population. This, however,

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assumes that good correlation exists between body measures whereas it has long been

understood that correlation between some body measures can be extremely weak.

Figure 1.1.4. Human head 3D modelling using SolidWorks 2014.

.

1.2 Problem statement

Based on existing literatures, it is shown that prior researches have attended

separately to understand the visual and vestibular mechanisms which affect human

balance, hence, the position of CG and head sensory systems have been anatomically

located. The important reason of CG being a center of the head is a strategic point in

studying dynamic and static balance, and in physics; it is an essential point for studying

static and dynamic movement. Although prior researches have studied the effect of head

sensory system and CG on human balance and movement but unfortunately, they have

not shown the mathematical relation between them. Furthermore, it’s important to

visualize these relations using a 3D model in order to draw the imaginary plane of

visual and vestibular system.

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1.3 Objectives of study

Concerning to find the mathematical relationship of the head CG and sensory

system on human balancing system, several objectives in this study were being listed.

The objectives of this study are listed as follows;

1- To investigate the anatomical landmarks of head sensory system which can

marked on the surface of head skin

2- To design an imaginary page in human head, which contains eyes and inner ears

for retaining the relation between these points and head centre of gravity

3- To simulate a 3D modelling of head and the imaginary.

4- To determine the mathematical relation and formula of the CG and head sensory

system

1.4 Significance of study

To date, there is no mathematical relation has been reported among head CG and

balance sensory systems of visual and vestibular. Therefore, an investigation of this

research seems essential in contributing to the gap of knowledge in the literature. The

newly formulated equation can be useful for biomechanical study of human balance

involving visual and vestibular systems. Together with a 3D modelling of human head

will provide new approach for further studies on human balance and positioning of head

and body.

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CHAPTER 2

LITERATURE REVIEW

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2.1 Human balance sensory system

The study on human balance dates back to 1452 – 1519 when Da Vinci established

human balance relations using mathematical methods. The Fibonacci number is φ≡ (a +

b) / b = a / b = 1.618 that has been known as Golden ratio (Dunlap & Dunlap, 1997). This

number is useful in many fields of science, particularly those related to human physical

design. The painting of human body by Da Vinci has inspired many scientists who are

interested to realise human body type, human stability, and human balance mechanism.

According to Da Vinci, balance is a product of the postural task and the

environment in which it is performed (Brent, 1989; Koo & Kim, 1995; Winter, 1995).

The characteristics of the task and the environmental context may alter the biomechanical

response strategies to maintain balance, and the central information processing

requirements and quantities. In biomechanics, balance is an ability to maintain the centre

of gravity of a body within the base of support with minimal postural sway. Balancing

requires concurrent processing of inputs from multiple senses, while the motor system

simultaneously controls muscle actions. The senses must detect changes of body position

with respect to the base, regardless of body or base movements.

Several studies have demonstrated that human standing posture is affected by

perturbations to balance sensory systems (Dichgans & Brandt, 1978; Manchester et al.,

1989; Posner & Petersen, 1989; Horak et al., 1990; Pozzo et al., 1990; Winter, 1991; Day

et al., 1997; Lacour et al., 1997; Carpenter et al., 2001; Creath et al., 2002) suggesting

that feedback control, based on perceived body motion, contributes to postural stability.

There is redundancy across these sensory systems and the organisation of these feedback

control mechanisms is not fully known. Also, there is some question as to whether

feedback alone is sufficient for human postural control (Taga, 1995; Allum & Honegger,

1998; Indovina et al., 2005; T. Mergner et al., 2009), although later studies have shown

that a postural control strategy based solely on sensory feedback can account for

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experimental findings involving a variety of proprioceptive and visual perturbations to

postural control (Pozzo et al., 1990; Day et al., 1997; Fitzpatrick & Day, 2004; Naito et

al., 2012).

The control of balance requires the integration of information from multiple

sensory and motor systems by the central nervous system (CNS). The eyes (visual system)

provide input regarding the body's orientation within the environment and about motion

within the environment. Balance receptors in the inner ear (the vestibular system) provide

information to the CNS about head and body movements. The position and motion

sensors of the muscles and joints, and the touch receptors of the extremities

(proprioceptive system) send signals regarding bodily position, particularly in relation to

the support surface. The CNS integrates all this data, determines the body's spatial

orientation, and sends appropriate neural messages to the motor system to activate

movements that will maintain equilibrium.

Looking at what has been studied; most researchers focus on functional aspects

by explaining and clarifying the balance factors individually and not in combination,

which lead to various proposed isolated mechanisms of these factors. In order to establish

relationships among the balance factors, scientists need a form of test that includes these

factors and measures the influences of each factor on the others as well as tests for

measuring the influences of these factors on human balance, so they designed many tests,

which cover all these issues.

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Figure 2.1. Human body balance mechanism, the role of sensory system and involving

parts.

2.2 Biomechanics of human balance

Many of the earlier studies concerning body and limb measurements ignored

biomechanics, but based on more recent knowledge, body characteristics affect postural

stability. A major impetus for anthropometric measurements has come from the needs for

technological development (Berg, 1989; Pozzo et al., 1990; Winter, 1995). The most

basic body dimensions are the distances between joints (Tinetti et al., 1988; Magnusson

et al., 1990; Allum et al., 1995; Winter, 1995), and an average set of distances expressed

as proportions of body height gives a good approximation of a body model.

Anthropometric factors should be considered in biomechanical modelling of the body

(Tinetti et al., 1988; Magnusson et al., 1990; Allum et al., 1995; Winter, 1995), in

planning a measurement and in assessing the results of measurements. Data based on

some new balance measurement systems can be normalised and related according to body

height (Kinney et al., 1996; Coast, 1997; B. L. Day et al., 1997).

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The biomechanical model can be used in, for example, segmental analysis

(Benvenuti et al., 1999; Kavounoudias et al., 1999), but the information of body

characteristics may also directly affect the measurement values. In the inverted pendulum

model (Nashner, 1985; L. I. Wolfson et al., 1986), a longer lever arm, e.g. longer height,

would cause a greater amplitude of movement than a shorter height. Besides, the support

surface size (foot size) is related to height (male – female). Body characteristics should,

therefore, also be considered in measurement settings, e.g. as far as marker placement in

measurements with motion analysis is concerned. The differences in body characteristics

have been assumed to influence the boundaries of individual postural stability, and this

variability may affect the selection of motor strategies to maintain postural balance

control (Nashner, 1985; Magnusson et al., 1990).

The different body heights of men and women have been assumed to contribute

to the poorer postural stability of men compared to women (Taga, 1995; Kinney et al.,

1996; Pai & Patton, 1997), and it is possible that the balance differences between men

and women are mainly due to their different anthropometrics. Typically, the postural

control of both genders has been assessed with platforms (Era et al., 1996), but there are

also motion analysis results showing differences in movement strategies between men

and women (Johansson & Vallbo, 1980; Lund & Broberg, 1983; Mackel, 1985; Nashner,

1985).

2.3 Human head planes and centre of gravity (CG)

Anatomy is often described in planes, referring to two-dimensional sections of

the body. A section is a two-dimensional surface of a three-dimensional structure that

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has been cut. A plane is an imaginary two-dimensional surface that passes through the

body. Three planes are commonly referred to in anatomy and medicine:

Three main planes cross the human head, namely, the Frankfort (transverse),

sagittal (sagittal), and coronal (frontal) planes (Clauser et al., 1969; Keshner & Peterson,

1995). The Frankfort plane passes through the inferior margin of the left orbit (the left

orbitale) and the upper margin of each ear canal or the external auditory meatus (the

porion). It is almost parallel to the ground. The sagittal plane is a vertical plane that

extends from the ventral (front) to the dorsal aspect (rear) and divides the head into right

and left halves. The coronal plane is a vertical plane that divides the head into ventral

(belly) and dorsal (back) sections (Clauser et al., 1969; Ringelstein et al., 1990; Koo &

Kim, 1995; Volinsky et al., 1997; Dougherty et al., 2003).

The head also contains an area called the head centre of gravity (CG), which is a

significant point for biomechanical analysis (McConnell et al., 1995; Willinger et al.,

1999; Funk et al., 2009; Yoganandan et al., 2009). Dempster (1955) reported that the CG

is located along a point in the phenoid sinus averaging 4mm beyond the anterior-inferior

margin of the sella; on the surface its projections lay over the temporal fossa on or near

the nasion-inion line at a point about 32% back from the nasion; it was equally distant

above the zygomatic arch and behind the malar fronto-sphenoid process. Winter and his

team (1995) demonstrated that CG landmarks are anatomically located above the right

and left infraorbital notches and at the superior edge of the right and left external auditory

meatus on the skin. These landmarks originate from the centre of the markers of the right

and left external auditory meatus. The +Z axis extends from the origin in a cephalad

direction to the plane formed by the +X axis and the line between the auditory meatus

markers at right angles. The +Y-axis extends from the origin toward the left ear to the X–

Z plane at right angles. This plane is known as the mid sagittal plane. The anatomical

location of the head and neck CG is “8mm anterior to the basion on the inferior surface

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of the base of Occiput or within the bone 24 ± 5 mm from the crest of the dorsum sella;

on the surface of the head a point 10 mm anterior to the supratragic notch above the head

of the mandible is directly lateral.” Clauser and his team (Clauser et al., 1969) reported

that the mean distances of the head CG are 46.4% below the vertex and 40.0% from the

occiput. Human balance and stability are affected by the physiological balance system,

nervous system, and reaction time. Previous studies emphasise the human head as the

main control centre of balance. The visual, vestibular, and proprioceptive systems

comprise the sensory system of physiological balance in humans, which is essential to the

maintenance of balance and stability.

2.4 Anatomical landmarks

When describing the position of anatomical structures, landmarks may be used to

describe location. These landmarks may include structures, such as the umbilicus or

sternum, or anatomical lines, such as the mid clavicular line from the centre of the

clavicle. The cephalon or cephalic region refers to the head. This area is further

differentiated into the cranium (skull), facies (face), frons (forehead), oculus (eye area),

auris (ear), bucca (cheek), nausus (nose), oris (mouth), and mentis (chin). The neck area

is called the cervicis or cervical region.

To further increase precision, anatomists standardise the way in which they view

the body. Just as maps are normally oriented with north at the top, the standard body

“map”. It does not matter how the body being described is oriented, the terms are used as

if it is in anatomical position. For example, a scar in the “anterior (front) carpal (wrist)

region” would be present on the palm side of the wrist. The term “anterior” would be used

even if the hand were palm down on a table.

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Eye: the palpebral fissure is elliptical in shape, and varies in form in different

individuals and in different races of humankind; normally it is oblique, in a direction

upward and lateral ward, so that the lateral commissure is on a slightly higher level than

the medial. When the eyes are directed forward as in ordinary vision the upper part of the

cornea is covered by the upper eyelid and its lower margin corresponds to the level of the

free margin of the lower eyelid, so that usually the lower three-fourths are exposed.

At the medial commissure are the caruncula lacrimalis and the plica semilunaris.

When the lids are everted, the tarsal glands appear as a series of nearly straight parallel

rows of light yellow granules. On the margins of the lids about 5 mm. from the medial

commissure are two small openings the lacrimal puncta; in the natural condition they are

in contact with the conjunctiva of the bulb of the eye, so that it is necessary to evert the

eyelids to expose them. The position of the lacrimal sac is indicated by a little tubercle,

which can be plainly felt on the lower margin of the orbit; the sac lies immediately above

and medial to the tubercle. If the eyelids were, drawn lateral ward to tighten the skin at

the medial commissure a prominent core can be felt beneath the tightened skin; this is the

medial palpebral ligament, which lies over the junction of the upper with the lower two-

thirds of the sac, thus forming a useful guide to its situation. On looking into the eye, the

iris with its opening, the pupil, and the front of the lens can be examined, but for

investigation of the retina, an ophthalmoscope is necessary. With this the lens, the vessels

of the retina, the optic disk, and the macula lutea can all be inspected.

On the lateral surface of the nasal part of the frontal bone the pulley of the

Obliquus superior can be easily reached by pushing the finger backward along the roof

of the orbit; the tendon of the muscle can be traced for a short distance backward and

lateral ward from the pulley.

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Ear: the various prominences and fosse of the auricula are visible. The opening

of the external acoustic meatus is exposed by drawing the tragus forward; at the orifice

are a few short crisp hairs which serve to prevent the entrance of dust or of small insects;

beyond this the secretion of the ceruminous glands serves to catch any small particles

which may find their way into the meatus. The interior of the meatus can be examined

through a speculum. At the line of junction of its bony and cartilaginous portions, an

obtuse angle is formed which projects into the antero-inferior wall and produces a

narrowing of the lumen in this situation.

The cartilaginous part, however, is connected to the bony part by fibrous tissue,

which renders the outer part of the meatus very movable, and therefore by drawing the

auricula upward, backward, and slightly outward, the canal is rendered almost straight.

In children, the meatus is very short, and this should be remembered in introducing the

speculum. Through the speculum, the greater part of the tympanic membrane is visible.

It is a pearl-gray membrane slightly glistening in the adult, placed obliquely to form with

the floor of the meatus an angle of about 55°. At birth, it is more horizontal and situated

in almost the same plane as the base of the skull. The membrane is concave outward, and

the point of deepest concavity the umbois slightly below the centre. Running upward and

slightly forward from the umbo is a reddish-yellow streak produced by the manubrium of

the malleus. This streak ends above just below the roof of the meatus at a small white

rounded prominence, which is caused by the lateral process of the malleus projecting

against the membrane. The anterior and posterior malleolar folds extend from the

prominence to the circumference of the membrane and enclose the pars flaccida. Behind

the streak caused by the manubrium of the malleus a second streak, shorter and very faint,

can be distinguished; this is the long crus of the incus. A narrow triangular patch

extending downward and forward from the umbo reflects the light more brightly than any

other part, and is usually described as the cone of light.

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2.5 3D and mathematical modelling of human head

Computational face spaces derived from different kinds of face representations

(2D pixel-based images (Kaleps et al., 1984; Kim et al., 1998; Yoganandan et al., 2009)

3D surfaces from laser scans (Cromwell et al., 2001; Yoganandan et al., 2006) may make

different predictions about the similarity/confusability of faces. More formally, the

distance between two faces in a face space based on 2D pixel-based images may be very

different than the distance between faces in a three-dimensionally based face space.

Before proceeding, it is worth illustrating briefly that computationally derived

face spaces can differ both quantitatively and qualitatively in the predictions, they make

about perceptual variations in facial appearance. For example, recent work illustrates that

the application of an automatic caricature algorithm to faces represented by their 3D

structure alters the age of a face; more than its distinctiveness (Chiu, 2005; Yoganandan

et al., 2009). In that study, faces were represented as vectors in a PCA-based face space

derived from a low level encoding of the 3D head structure.

A generic caricature applied to a computationally derived face space based on a

3D representation of faces produced a very salient change in the age of faces. Applied to

a 2D configural representation of faces, a similar trajectory in the face space produced

more salient changes in the distinctiveness of faces. Thus, when implementing simple

algorithms for manipulating the appearance of faces, the nature of the features underlying

the face space has important perceptual consequences.

The relationship between human image perception and artificial image

manipulations is a central problem for many image-processing applications. An

understanding of this will allow us to change images selectively along even relatively

abstract specific perceptual dimensions. For the problem of image search in databases,

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the mapping of human image descriptions onto formal image representations can increase

the efficiency of the search.

A computationally defined face space based on a representation of how the faces

differ in their 3D shape and 2D texture from the average face. The primary manipulation

consisted of altering the length of the face vectors in a selected subspace of the general

face space. This manipulation is opposite to that carried out normally in automated

caricature generators. Faces increased in attractiveness and decreased in apparent age

with shape or texture normalisation. Additionally, it showed that although the

normalisation procedure simultaneously affects both the age and attractiveness of the

faces, the perception of these two facial attributes was not synonymous.

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CHAPTER 3

METODOLOGY OF RESEARCH

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3.1 Approach and selection of research methodology (research design)

In this explorative research a new approach of using digital optical photography

(PH) to measure the distance and angle between human head surface landmarks instead

of using Computer Tomography (CT) or Magnetic Resonance Imaging (MRI) images was

presented. Hence, the mathematical relation among head balance sensors and computer

3D modelling of these sensory systems and heads CG were derived. By using this method

the new imaginary plane of human head balance factors was also presented.

This research was conducted as a prospective cross-sectional study with

convenience sampling. The CT images uses as a reference images to find out the

anatomical location of visual and vestibular system of human head. The PH images from

patients were used to select these anatomical landmarks on the surface which is used to

design the 3D modelling of human head. In addition to PH images measurement

processes, the anthropometric devices were used to measure the angle and distance among

the landmarks.

3.2 Subjects

The subjects for this study were patients who had been referred for brain CT by

an imaging specialist at the University of Malaya Medical Centre from January to April

2013. Male adults (ages 19 to 25) were selected to participate in this study. All

participants provided their informed consents for the CT scan to comply with the hospital

policy and regulations. The exclusion criteria were deformity in head, disorders of the

visual and vestibular systems, and brain tumour. A total of 72 young male and female

individuals were screened for this study, 12 of whom were excluded because of low-

resolution CT images (n = 60).

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3.3 Ethical concern and hospital policy

Since the study involves CT images while the subjects were patients who had been

referred for brain CT by an imaging specialist, a medical ethics approval was acquired by

researchers at the University of Malaya Medical Centre as mandatory standard hospital

policy. All patient fill the volunteer form which include the informed consent for the

scanning.

3.4 Flow chart

For doing this research the new method were designed which divided to some

steps for collecting the data. This flow chart was shown the research method and data

collection parts.

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Figure 3.4. Flowchart showing the research process.

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3.5 Computer Tomography

The CT images were captured using the CT Siemens (Germany) with the least-

quality base of 0.75 and H41s. The images were then transferred to the Syngo

workstation, which allowed the researcher to mark points on the images, measured the

distance between the points, and determined the angle between the points. The software

generates layer-by-layer 2D images from 3D views. Three views of the CT images (i.e.,

top, left, and right) were used to locate the exact points of the visual and vestibular

systems.

Syngo workstation is a special CT images software which it was calibrated. It

means by zooming in or out the distance, angle and other measurement parameter were

never changed and the measurement is being as a real measurement parameter. By using

this software the researcher can be able to select or mark the exact point which he need.

From each side (left and right) the inner ear and midpoint of visual were marked. Hence

this marking were used as a reference point of anatomical landmarks for photography and

anthropometric devices.

After marking the collected CT images for the vestibular and midpoint regions of

each eye. Next, the distance between the selected points was measured to compare with

the photograph of the referred landmarks. The line between the visual and vestibular

systems was drawn which is known as balance factor line (BFL). Moreover, the angle

between the line of visual–vestibular markers, known as the line of balance and Frankfort

planes (AVVF), were logged for both of the left and right sides (Figure 3.5).

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Figure 3.5. The left and right side of CT images.

3.5.1 Determining anatomical landmarks

The inner ear area was selected instead of the vestibular because the vestibular is

too small, and the area cannot be distinguished on CT images. To select the inner ear area

in the top view, the CT image layers was rotated to view both sides (left and right) in one

layer. Hence, enlarging the images was necessary to achieve the most accurate point of

the inner ear area. For selecting this area in left and right side, zooming in the images 70

% it seems necessary. Selection of midpoint for each side were done by using the ability

of Syngo workstation software which were allowed the researcher find the exact selection

of top view on each side.(synchronisation selecting points)

To find the midpoint of the eye, lines were drawn from the top to the bottom of

the eye. The software allow researcher to find the midpoint of the drawing line which

were used to mark the eyes midpoints.

The inner ear and visual marks were used as a reference landmarks of human head

balance factors which then will use to mark these sensory system on the surface for taking

the photography and doing the measurement by anthropometric devices.

3.6 Photography

Photographs (PH) of the patients were taken using a digital Nikon 10 MP camera.

The camera was placed 100 cm in front of the centre of a rotatable chair on a professional

camera stand(L. Wolfson et al., 1990). The bubble balance level of the camera stand was

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set at zero position Figure 3.6. The captured photos were studied using CorelDRAW X6

to determine the distance and angle between the eyes and vestibular landmarks. Based on

finding the exact point of the visual and vestibular system on CT images, the coloured

markers were attached to the head surface to highlight anatomical landmarks.

Figure 3.6. The camera and seat position.

The front, left, and right views of the patients were taken while they were sitting

on a revolving chair. The photos were taken without optical or digital zooming, with the

camera set on auto mode and auto capture (the timer was set on two seconds). The height

of the camera was set based on the height of the patients. Although the camera height

changed, the centre of the camera was ensured to coincide with the centre of the chair.

Thus, the distance between the camera and the chair remained at 100 cm. The centre of

the camera guidelines conformed to the midlines of the eyes.

For selecting the centre of markers, the photos were then zoomed by 75% in

CorelDRAW X6 software. The distance between these two landmarks was also measured

(in centimetres), and a line was drawn between these points. Subsequently, the Frankfort

plane was drawn for each side to measure the angle between the visual–vestibular

landmarks and this plane (in degrees).

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3.6.1 Determining anatomical landmarks

The photos were transferred to CorelDRAW X6. The following landmarks were

marked with the marker prior to the analysis: the caruncula lachrymal (eye corner) and a

point 1 mm in front of the anterior notch above the tragus (vestibular point) (Figure

1.1.2.1).

These landmarks on the surface were placed on the point which is shown in Figure

1.1.2.1 based on the finding of CT images that were used as a reference for selecting the

landmarks. By using the CorelDRAW X6 the centre of each surface marker were marked

in the software again to allow the researcher for measuring the distance and angle between

these points.

3.7 Anthropometric measures

Apart from CT and photographic measurements, anthropometric devices, namely,

a goniometer (ATB, Malaysia) and measuring tape (FISCO, Taiwan) were also used. The

direct measurements (surface marking) of the distance and angles from identified

landmarks which were used for photographic analysis were recorded.

A measuring tape and a goniometer were used to determine the distance and the

angle between the landmarks, respectively. The horizontal circumferences of the middle

of the head and neck and the vertical circumference of the surface distance between the

right and left tragion passing over the top of the head and the tip of the chin were obtained

by using the measuring tape. These values were used to calculate the volume of the head

as shown in (Figure 3.7). The head volume was calculated using V = 4/3 πabc.

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Figure 3.7. The head volume calculation (V = 4/3 πabc).

3.8 Computer modelling of human head

In this study, combination of two techniques (polygonal modelling and curve

modelling) was applied for drawing the 3D modelling. Polygonal modelling, points in 3D

space, called vertices, were connected by line segments to form a polygonal mesh. The

vast majority of 3D models today are built as textured polygonal models, because they

are flexible and because computers can render them so quickly. Curve modelling, surfaces

are defined by curves, which are influenced by weighted control points. The curve follows

(but does not necessarily interpolate) the points. Increasing the weight for a point will

pull the curve closer to that point. Curve types include non-uniform rational B-spline

(NURBS), splines, patches and geometric primitives. The average of collecting data were

used to design a 3D model of the human head using SolidWorks version 2014, then the

average values of the head surface parameters from the photographic method were

computed to remodel the head structure. Finally the volume of the head was corrected

using the anthropometric data. The visual–vestibular landmarks of the sensory system

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were identified on the model, and the imaginary plane that connects these landmarks was

illustrated. The head CG was depicted as a hollow sphere in this model and the connecting

lines between CG (middle of the hollow sphere) and the imaginary plane were drawn

resulting in a pyramidal structure (Figure 4.7.3).

3.9 Mathematical relationship

Based on finding with CT images, photography and anthropometric devices the

distances are equal between the visual and the vestibular systems on the left and right

sides; thus, an isosceles trapezoid is generated by connecting the points.

By using the geometric relation of isosceles trapezoid the angles and distance

between these points can be calculated which this calculation were led to bring the

mathematical formulas. These mathematical relation were calculated based on the

formulas of isosceles trapezoid. Hence by using the COG place and these sensory system

place the mathematical relation among them were calculated by using Math lab Software.

3.10 Statistical analysis

For data analysis, the Graph Pad Prism version 6 was used. One-way ANOVA

and Bonferroni test for match pairs of the CT images, photos, and anthropometric tools

were performed with P < 0.05. The Pearson product-moment correlation coefficient was

used with 95% confidence interval. The intraclass correlation coefficient (ICC) reliability

was determined to compare the data collected by two different researchers. Furthermore,

limitation of agreement (LOA) was calculated using the Bland-Altman test on SPSS

version 24.

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CHAPTER 4

RESULTS

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4.1 Demographics data

The subjects of this research were young adult male and female (age = 22 ± 3

years old), with average height (165 ± 6.25 cm) and weight (65 ± 9.36 kg). These were

patients who had been referred by specialist for CT scans. For comparison between

gender, equal number of subjects from each gender was selected (n = 60; male = 30 and

female = 30). Table 4.1 shows means and standard deviations (M ± SD) of subject’s

demographic data. From the data, no significant difference was found between genders,

thus it was assumed that all subjects have similar characteristics. All subjects were

between 19 to 25 years old.

Table 4.1.1 Demographic of subject’s characteristics for each gender presents in mean

and standard deviation.

Male Female

(n = 30) (n = 30)

Age (year) 22 ± 3 22 ± 3

Height (cm) 170 ± 7.45 160 ± 5.05

Weight (kg) 70 ± 10.42 60 ± 8.32

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4.2 Distance and angle from CT images

After analysing the CT images using the Syngo software by placing the markers

on selected points on the images, the distances and angles measured between the selected

points are presented in Table 4.2.1.

Table 4.2.1 Parameters obtained from CT scan images.

Male Female

Right Left Right Left

DVV1 (cm) 8.16 ± 0.35 8.16 ± 0.35 8.16 ± 0.37 8.16 ± 0.37

AVVF2 (o) 11.80 ± 0.25 11.80 ± 0.25 11.80 ± 0.24 11.80 ± 0.24

TBD3 (cm) 3.25 ± 0.18 3.25 ± 0.18 3.25 ± 0.16 3.25 ± 0.16

THVID4 (cm) 7.87 ± 0.26 7.87 ± 0.26 7.56 ± 0.23 7.56 ± 0.23

THVED5 (cm) 12.68 ± 0.32 12.68 ± 0.32 12.57 ± 0.29 12.57 ± 0.29

BHVED6 (cm) 14.62 ± 0.65 14.62 ± 0.65 14.58 ± 0.54 14.58 ± 0.54

1 DVV = Distance between the visual and vestibular lines 2 AVVF = Angle between the visual-vestibular lines and the Frankfort plane 3 TBD = Distance from top to bottom of eye 4 THVID = Distance between the top head (forehead) to the eye 5 THVED = Distance between the top head (forehead) to the ear 6 BHVED = Distance between the head bottom and the ear

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4.3 Distance and angle from photography

The PH images were taken from front, left and right views of each patient with

the markers placed on the surface of head landmarks. By transferring the PH images to

CorelDraw, measurements of the distance and angles are tabulated in Table 4.3.1.

Table 4.3.1 Parameters obtained from photography (PH) images.

Male Female

Right Left Right Left

DVV1 (cm) 8.11 ± 0.58 8.11 ± 0.58 8.11 ± 0.55 8.11 ± 0.55

AVVF2 (o) 11.65 ± 0.45 11.65 ± 0.45 11.65 ± 0.42 11.65 ± 0.42

TBD3 (cm) 3.20 ± 0.20 3.20 ± 0.20 3.20 ± 0.16 3.20 ± 0.16

THVID4 (cm) 8.13 ± 0.36 8.13 ± 0.36 8.10 ± 0.37 8.10 ± 0.37

THVED5 (cm) 13.40 ± 0.24 13.40 ± 0.24 13.30 ± 0.29 13.30 ± 0.29

BHVED6 (cm) 15.32 ± 0.42 15.32 ± 0.42 15.22 ± 0.44 15.22 ± 0.44

1 DVV = Distance between the visual and vestibular lines 2 AVVF = Angle between the visual-vestibular lines and the Frankfort plane 3 TBD = Distance from top to bottom of eye 4 THVID = Distance between the top head (forehead) to the eye 5 THVED = Distance between the top head (forehead) to the ear 6 BHVED = Distance between the head bottom and the ear

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4.4 Distance and angle using anthropometric devices

The anthropometric devices were used to measure the distances and angles of

surface markers of head landmarks. The results are presented in Table 4.4.

Table 4.4.1 Parameters obtained using anthropometric devices.

Male Female

Right Left Right Left

DVV1 (cm) 8.08 ± 0.41 8.08 ± 0.41 8.08 ± 0.45 8.08 ± 0.45

AVVF2 (o) 11.6 ± 0.48 11.6 ± 0.48 11.6 ± 0.43 11.6 ± 0.43

TBD3 (cm) 3.21 ± 0.19 3.21 ± 0.19 3.21 ± 0.13 3.21 ± 0.13

THVID4 (cm) 8.10 ± 0.36 8.10 ± 0.36 8.08 ± 0.37 8.08 ± 0.37

THVED5 (cm) 13.36 ± 0.24 13.36 ± 0.24 13.16 ± 0.29 13.16 ± 0.29

BHVED6 (cm) 15.29 ± 0.42 15.29 ± 0.42 15.09 ± 0.39 15.09 ± 0.39

1 DVV = Distance between the visual and vestibular lines 2 AVVF = Angle between the visual-vestibular lines and the Frankfort plane 3 TBD = Distance from top to bottom of eye 4 THVID = Distance between the top head (forehead) to the eye 5 THVED = Distance between the top head (forehead) to the ear 6 BHVED = Distance between the head bottom and the ear

4.5 Statistical analysis

4.5.1 Correlations

The Pearson correlation was applied between CT and PH for measures: distance

between the visual and vestibular lines, angle between the visual-vestibular lines and the

Frankfort plane and distance from top to bottom of eye which are shown in Table 4.5.1.

The Confidence interval set 95% and two tailed P value is (DVV = 0.001359,

AVVF = 0.004371 and TBD = 0.003449) which is present no significant different.

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Table 4.5.1 Pearson correlation (r value) between CT and PH images.

DVV1 AVVF2 TBD3 THVID4 THVED5 BHVED6

DVV1 0.995 - - - - -

AVVF2 - 0.998 - - - -

TBD3 - - 0.997 - - -

THVID4 - - - 0.879 - -

THVED5 - - - - 0.884 -

BHVED6 - - - - - 0.867

1 DVV = Distance between the visual and vestibular lines 2 AVVF = Angle between the visual-vestibular lines and the Frankfort plane 3 TBD = Distance from top to bottom of eye 4 THVID = Distance between the top head (forehead) to the eye 5 THVED = Distance between the top head (forehead) to the ear 6 BHVED = Distance between the head bottom and the ear

4.5.2 Analisis of variance (ANOVA)

Two way ANOVA was applied determine the interaction between gender (male

and female) and methods used (CT, PH and anthropometric device). Results show that

there was no effect of gender (F = 0.884 and t = 0.7587 and p = 0.567), and the data was

collapse and one-way repeated measured was then used to analyse the data.

One way ANOVA was applied for comparing the differences in distances and

angle in based on the three methods. Table 4.5.1 presents the values of angle

measurements with different devices on male/female for both side.

4.5.3 Intraclass correlation (ICC) between ratters

To determine the reliability of the measurements, the ICC between ratters was

calculated. The ICC the result was 0.965 with the F-test 56.303, df1 = 29, df2 = 29.

PH

CT

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4.6 Imaginary plane

The imaginary plane of the human head balance system was constructed using

information obtained from the visual and vestibular anatomical landmarks. From the

sagittal view, this plane crossed the Transverse plane with an average angle of 11.65 ±

0.25°. The repeatability of measurements between the two ratters using the ICC was 0.96

and 0.97 for the photos and anthropometric devices respectively. Figures 4.6.1, 4.6.2, and

4.6.3 show the different view of imaginary page of balance factors and transverse plane.

Figure 4.6.1. Sagittal view of Planes (Plane 9 = transverse, trapezoid = imaginary plane).

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Figure 4.6.2. Top view of Planes (Plane 9 = transverse, trapezoid = imaginary plane).

Figure 4.6.3. Front view of planes (Plane 9 = transverse, trapezoid = imaginary plane).

Based on the findings of this study which proved that the distances between the

anatomical landmarks of visual and vestibular for both sides (left/right) were similar,

therefore an isosceles trapezoid was proposed as shown in Figure 4.6.4. In the discussion

section equations will be derived based on the proposed mathematical relation.

Eyes

Vestibular

α α

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Figure 4.6.4. Schematic view of imaginary plane of human head balance factors.

4.7 3D modelling

This study proposed a new 3-D model of the human head that recognises the head

CG through the visual and vestibular landmarks. This research utilised three methods in

the process; CT scan, photography, and anthropometry which findings were then

integrated into SolidWorks software for 3D modelling as close as possible to the real

head. Figures 4.7.1 and 4.7.2 show the general view of the 3D model which the CG, visual

and vestibular landmarks were highlighted. Figure 4.7.3 shows the pyramid which the top

was CG and base the imaginary plane of connecting the visual-vestibular landmarks. To

calculate the parametric mathematical relation among CG, visual and vestibular points

the connecting, height and midlines were drawn for each side of the pyramid.

Figure 4.7.1. Lateral view of 3-D model.

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Figure 4.7.2. Left and top view of 3D model.

Figure 4.7.3. Close-up view of CG and visual-vestibular pyramid.

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CHAPTER 5

DISCUSSIONS

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5.1 Introduction

This chapter discusses the mathematical relationships (distances and angles)

between visual and vestibular head balance sensory systems. Briefly, three methods were

employed to locate the visual–vestibular landmarks namely the CT images, digital

photography and anthropometric devices. The study also aimed to prove that an ordinary

digital photography is a reliable tool in locating the anatomical landmarks as compared

to a sophisticated CT images. The mathematical relationships were then used to establish

a new plane connecting the visual and vestibular landmarks. The new visual-vestibular

plane was then explained in relation to the Frankfort plane (transverse plane) and CG.

Finally this study introduced a new 3D model of the human head illustrating the

relationship between the proposed plane and CG.

5.2 Anatomical landmarks and the proposed plane.

Based on Tables 4.2.1, 4.3.1 and 4.4.1, the major finding of this study showed the

distance between; the visual and vestibular (both left and right) was 8.11 ± 0.58 cm, while,

the angle between the visual-vestibular line and the Frankfort plane was 11.65 ± 0.45o.

The outcomes of the three methods employed were similar to each other (p > 0.05), which

suggests ordinary digital photography and anthropometric devices are compatible to CT

images.

The landmarks of the human head and their connections, including the bitragion-

coronal, bitragion-minimum frontal, bitragion-subnasale, and bitragion-menton, have

been previously studied. The reference point for all the measurements was the tragion

(auris) (Hamalainen & Sarvas, 1989; Grosbras et al., 1999; Yoganandan et al., 2006). In

this study, the frons (forehead), oculus (eye area), auris (ear), and mentis (chin) were

designated as anatomical landmarks, which cover a wider area of the head (Walker et al.,

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1973; T. Pozzo et al., 1991; Collignon et al., 1995; Keshner & Peterson, 1995; McConnell

et al., 1995; Cromwell et al., 2001; Yoganandan et al., 2009).

This study applied a new approach using the head anatomical landmarks to cover

some of the weaknesses of previous methods. MRI and CT are hazardous for the human

health; for example, exposure to ionising radiation can increase the risk of cancer, and

high doses can cause serious damage, including radiation burns. Moreover, these methods

are costly for the patients. Collecting data through CT scan is not easy because it

necessitates bio-imaging knowledge (Broadbent, 1931; George & Fabian, 1991;

Willinger et al., 1999; Karch, 2004; Mikaeloff et al., 2004; Funk et al., 2009; Haruna et

al., 2010). Analysing CT images requires special equipment and software where the 3D

images are transferred to 2D layers and manipulated to obtain the best view to locate the

landmarks. These procedures are time consuming and complicated. The new method used

in this study can reduce the time and cost, making the study of human head landmarks

easier and safer. Currently, with the advent of modern devices and software, researchers

not only measure the distance between these points but also the angle. Hence, this study

introduced a new approach to measure the distance and angle on photos taken using an

ordinary digital camera. One main reason for using these anatomical landmarks is that

these points can be easily located on the human head surface (Wang et al., 1996; Grosbras

et al., 1999; Klose & Sollmann, 2000; Kähler et al., 2002; Karch, 2004; Mikaeloff et al.,

2004; Chiu, 2005; Funk et al., 2009; Yoganandan et al., 2009). Meanwhile, some of the

points used in previous research were modified and improved. In the future, the

researchers may use the average angle between the visual–vestibular landmarks and the

Frankfort plane as anatomical landmarks to represent the sensory systems. The CT images

were used as reference to validate the new method. A comparison of the collected data

by two researchers showed that the new method is strongly reliable.

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Research on planes associated with head and neck dates back to the 1950s when

the sagittal, coronal, and Frankfort planes were first introduced (Broadbent, 1931;

Hamalainen & Sarvas, 1989; McConnell et al., 1995; Chancey et al., 2007; Yoganandan

et al., 2009). Although prior research were find the junction of this three plane were

placed of the CG which most researches used CG for biomechanical analysis of head

movements and they have shown that the geometric location of the head CG is close

proximity to the visual and vestibular systems, but they did not describe the mathematical

relation between CG and these sensory system. Hence, the head sensory balance plane

was not described. (Winter, 1995; Wang et al., 1996; Dumoulin et al., 2000; Klose &

Sollmann, 2000; Kähler et al., 2002). In this study, the oculus (eye area) and auris (ear)

were the anatomical landmarks from both left and right of the head that connect and form

the new proposed plane (Winter, 1995; Grosbras et al., 1999; Willinger et al., 1999).

The photograph and direct measurement methods introduced in the current study

can reduce the time and cost. Studying human head sensory system landmarks is easier

and safer with the new methods compared to the abovementioned methods. The CT

images were used as a reference to validate the new methods. Comparison of the collected

data by the two researchers indicated the strong reliability of the method. Interestingly,

comparison of the CT images, photographs, and anthropometric tools showed no

statistical difference which is shown in Table 4.5.1. Hence, it is clear that using plane

photography and anthropometric tools produce reliable results (ICC was 0.970 for the

photos and 0.960 for the anthropometry tools, the LOA was 0.302 for the photo and 0.294

for anthropometry tools).

With modern devices and software, researchers can measure the distance and

angle between the anatomical points. Hence, the new methods introduced in this study

can be used to measure the distance, angle, and planes from the obtained photos using a

standard digital camera and software. These anatomical landmarks were used because

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they can be easily located on the surface of the human head. Some of these points have

been used in previous studies but were modified and improved in this study (Broadbent,

1931; Chiu, 2005; Funk et al., 2009; Haruna et al., 2010).

5.3 3D modelling of human head

Previous studies showed that the head CG is related to the visual and vestibular

systems. Nonetheless, none of these works addressed the sensory balance plane of the

human head, to the author’s knowledge (Volinsky et al., 1997; Dumoulin et al., 2000;

Chiu, 2005; Broekhuis et al., 2009).

By using the anatomical landmarks and average of data measurement, the

polygonal model of head were drawn which the curve model help to point the CG and

create skins as much as possible to real average of measurement. Figure 5.4.1 shows the

polygonal of this model and Figure 5.4.2 shows the curve model.

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Figure 5.3.1. Polygonal model of human head.

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Figure 5.3.2. Curve model of human head.

The 3D modelling of the actual human head or body may be useful for future

research. This model can help researcher to better understanding of human balance

factor position and may led to farther study about the relation of geometric position of

sensory system and human balance mechanism.

5.4 Mathematical model between human head factors

This 3D model of the head was designed preciously based on the results obtained

from the mathematical relations among the sensory systems of the head which is shown

in Figures 4.7.3. Figure 5.4.1 illustrates the geometric locations of the visual–vestibular

and the CG. The resultant shape is pyramidal; the base is an imaginary plane of the

sensory system of the head, and the apex is the CG.

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The distances are equal between the visual and the vestibular systems on the left

and right sides; thus, an isosceles trapezoid base is generated by connecting the points.

The following mathematical formula is obtained from the geometric relation of the

triangle and the relation of the angle:

tan𝛽1 =𝐴

𝐵, tan𝛽2 =

𝐵

𝐶 𝑡𝑎𝑛𝛽1 + 𝑡𝑎𝑛𝛽2 = 𝑡𝑎𝑛𝛽 → 𝑡𝑎𝑛𝛽 =

𝐴

𝐵 +

𝐵

𝐶 → tanβ =

𝐴𝐶+𝐵2

𝐵𝐶

E (1)

Figure 5.4.1. Imaginary plane. Imaginary plane of the head sensory system. Yellow

circles are visual and orang circles are vestibular.

The 𝛽 is the degree of the visual–vestibular line and the coronal plane obtained

by measuring the distance between the anatomical landmarks of eye-to-eye and eye-to-

ear. By deducing 𝛽 at 90 , we calculated the angle of the visual-vestibular line and

sagittal plane as follows:

𝛽′ = 90 − 𝛽. E (2)

From the visual side, the angles are obtained as follows:

tan𝛼1 =𝐵

𝐴, tan𝛼2 =

𝐶

𝐵 𝑡𝑎𝑛𝛼1 + 𝑡𝑎𝑛𝛼2 = 𝑡𝑎𝑛𝛼 → 𝑡𝑎𝑛𝛼 =

𝐵

𝐴 +

𝐶

𝐵 → tan𝛼 =

𝐵2+ 𝐴𝐶

𝐴𝐵,

E (3)

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The 𝛼 is the degree of the visual-vestibular line and the coronal plane. Hence, by

deriving 𝛽 at 90 , we compute the angle of the visual–vestibular line and sagittal plane:

𝛼′ = 90 − 𝛼. E (4)

We calculate the angle between the visual–vestibular line and the coronal, sagittal,

and Frankfort planes according to the distance between the anatomical landmarks of the

visual and vestibular systems. The angle of the visual or vestibular point from each main

plane can be calculated by measuring the distance of visual-vestibular, eye to eye and ear

to ear points.

5.5 Limitation of study

Since this study employed participants among young adult population,

generalising the findings may not be appropriate. Independent studies using population

with different age groups are then warranted.

Sample size of this study was not large due to the number of patients agreeable to

participate in this research. Getting patients who need to do whole brain CT scan was not

easy, in addition they had to be free of any illness of visual-vestibular system as well as

deformity of head.

5.6 Future study

In future studies, the researchers may use the imaginary plane based on the

visual- vestibular landmarks as a human head balance plane which in studies related

with biomechanical analysis of human movement and stability. Hence it could be apply

for athletics for improving the balance and stability, which may led to find out better

technical performance while they doing the act. For example in badminton game, which

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is need focus on shuttle, the head movement have essential role. This new method can

help on greater analysis of movement and figure out more detail of mistake technical.

5.6 Practical application

Current study proposed a new method (photography) for studying the anatomical

landmarks of head sensory systems to cover the weaknesses of other methods that are

expensive, hazardous and not user friendly. This method not is not only cheaper but also

it is a green way to do research on human body.

5.7 Conclusion

A new method was introduced to identify the head balance plane with the intent

to find out the mathematical relations between the human head balance factors and

estimate the algorithm of human balance. Although the prior research used several

methods for finding the human balance factors, for the first time an imaginary plane of

human head balance is introduced. The new photographic method and anthropometry

tools can be easier, cheaper and safer for human. The finding of this study support

strongly the distance and angle between eye and ear in both gender are equal. Hence there

is no difference among races as well. The following mathematical formula is obtained

from the geometric relation of the triangle and the relation of the angle:

tan𝛽1 =𝐴

𝐵, tan𝛽2 =

𝐵

𝐶 𝑡𝑎𝑛𝛽1 + 𝑡𝑎𝑛𝛽2 = 𝑡𝑎𝑛𝛽 → 𝑡𝑎𝑛𝛽 =

𝐴

𝐵 +

𝐵

𝐶 → tanβ =

𝐴𝐶+𝐵2

𝐵𝐶 .

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